Apparatus for the production of metal strip from metal powder



Jan. 26, 1960. R. P. PERKS APPARATUS FOR THE PRODUCTION OF METAL March 5,

INVENTOR.

BY (a W APPARATUS FOR THE PRODUCTION OF METAL STRIP FROM METAL POWDER Roy Philip Perks, Water Orton, Warwicltshire, England, assignor to The International Nickel Company, Inc, New York, N. a corporation of Delaware Application March 5, 1957, Serial No. 644,048

2 Claims. (Cl. 18-9) The present invention is directed to an apparatus for producing metal strip by the direct compression or compacting of metal powder and, more particularly, to a method for the direct rolling of metal powder to flat strip having a width in excess of about one inch and being free of frilling along the edges upon subsequent sintering, cold rolling and intermediate annealing to remove porosity.

It is known to form metal strip from metal powder by a series of steps. In the first step, the powder is fed between a pair of cylindrical rolls having their axes arranged in a plane which may, for example, be horizontal and which compact the powder into a continuous strip having suflicient mechanical strength to withstand a limited amount of further handling. The compacted strip is next sintered by passage through a furnace at a high temperature and the sintered strip, which is still porous, is then subjected to a series of cold rolling operation, with intermediate annealing stages, to reduce it to a dense, non-porous strip.

In the first step, the powder has hitherto been fed from a hopper directly into the nip of the roll, or alternatively onto one roll, which as its revolves carries the powder into the nip of the roll as a layer uniform in thickness throughout its width. These methods give satisfactory results in making narrow strip with a width of up to about one inch. As the width of the strip produced is increased, for example, to about six inches, it is found that the edges of the strip tend to form into frills to an increasing extent in the course of subsequent cold rolling. This effect is aggravated if, in order to avoid contamination of the porous material by lubricant, the cold rolling is carried out using unlubricated rolls. Further attempts to cold roll such frilled strip only lead to very severe distortion and even splitting of the strip, and no convenient way of restoring it to the desired flat state is known.

It is an object of the invention to provide an apparatus for directly compacting metal powder into metal strip exceeding about one inch in width such that the resulting compacted strip can be brought to a substantially nonporous state by cold rolling and annealing while remaining flat and being free of frilling along the edges.

It is a further object of the invention to provide an improved apparatus adapted to control the flow of metal powder into the compactingrolls such that fiat metal strip is produced in widths exceeding about one inch and frilling along the edges of the strip is avoided on subsequent sintering, cold rolling and annealing.

Other objects and advantages of the invention will become apparent from the following description taken in conjunction with the accompanying drawing in which:

Figure 1 depicts a side elevation in section of a rolling mill adapted to roll metal powder into'metal strip and being provided with powder feeding means contemplated in accordance with the invention;

Figure 2 depicts a section in elevation taken along the section 2-2 shown in Figure 1; and

Figure 3 depicts a plan view of the apparatus shown in elevation in Figure l.

, powder used are factors.

c 2,922,189 Patented Jan. 26, 1%60 According to this invention, the desired axial distribution of the powder is eitected by appropriate shaping of two hoods shaped to follow approximately the cylindrical contour of the roll surface and define a gap immediately above the bite or nip of the rolls. It is known that two such partly-cylindrical hoods may be used to control the amount of powder fed to the roll gap (or nip of the rolls). In the hoods previously proposed, the lower edges have been parallel to the roll axes. The invention consists in shaping these edges as arcs of circles or otherwise so that the gap between them is greatest at the middle of each hood and decreases in both outward directions.

One form of apparatus contemplated in accordance with the invention is depicted in Figures 1, 2 and 3 of the drawing, wherein Figure 1 depicts the elevation taken at the section 11 of Figure 3 and Figure 2 depicts the elevation taken at section 22 of Figure 1. In the drawing, 1 and 2 are the compacting rolls and 5 is a hopper for holding powder to be rolled by passage between rolls 1 and 2. The hopper 5 is positioned so that the center line thereof is substantially coincident with the center line of the rolls 1 and 2 as illustrated in Figure 3. The lower face of hopper 5 is formed by hoods 3 and 4 which are partly cylindrical in section and which are adapted to bear against the surfaces of compacting rolls 1 and 2. The edges 6 and 7 of the hoods are shown in the drawing as being concave in form such that said edges are further apart in the region of the longitudinal center of the roll gap (and of the hopper) as compared to the region toward the edges of the roll gap and of the hopper 5. It will be seen from the drawing that hoods 3 and 4 in effect provide for feeding a comparatively greater amount of powder through the roll nip orgap toward the longitudinal center of the rolls than toward the edges of the rolls. The hoods 3 and 4 preferably are made of metal sheet which is as thin as possible consistent with mechanical strength. The edges 6 and 7 of the hoods preferably are chamfered as shown in the drawing to assist the smooth flow of powder through the nip or gap of the rolls.

It is to be understood that the distribution of the powder feed into the roll gap at various portions therealong is dependent upon the contour which is applied to the edges 6 and 7 of hoods 3 and 4. The exact edge contour of the hoods to insure the production of flat, sound, dense strip free from frilling along the edges in widths exceeding about one inch is of course dependent upon a number of factors. Thus, the bulk density and flowing power of the Again, it has been found that the surface of the compacting rolls tends to become polished with use and this effect will influence the amount of powder carried into the roll gap between a given pair of rolls at a given point of their width since a higher degree of polish on the rolls will cause a lesser amount of powder to be fed therethrough. Accordingly, it will be seen that the exact contour applied to the edges of the hoods must be sufficient to insure that frilling of the cornpacted strip is prevented upon subsequent cold rolling and annealing without permitting such overcompensation that cupping of the strip occurs during subsequent cold rolling, i.e., without permitting excessive metal in the center zone.

I have found that when the conventional uniform feed of powder is used the powder tends to be forced from the center to the sides of the rolls during the initial compacting, giving rise to a band of metal of higher density along each edge of the strip. As soon as the porosity of the strip has been reduced by cold rolling to such an extent that the effect of the cold work is to elongate the metal strip as well as to eliminate porosity, the difference in density across the width of the strip leads to differential elongation of the center and edge zones, which shows itself as frilling of the edges. The extra initial supply of powder in the center of the strip compensates for this tendency for the powder to be forced outwards during compacting and avoids the formation of zones of high density along the .edges of the strip. Instead, by

feeding additional powder to the compacting rolls to form change in density across the width should be smooth.

When this preferred strip is cold rolled the increased density in the central zone assists in the production of a flat product.

It will be appreciated that in accordance with the invention metal strip can be produced in any desired length since it is only necessary to continue feeding powder to the mill in order to produce the desired amount of strip.

Furthermore, it is to be pointed out that there is no necessity for employing any sort of carrier strip for the purpose of conducting the powder through the compacting rolls. The compacted powder emerging from the rolls has suflicient strength that it can be handled in subsequent desired annealing and/ or rolling operations designed to reduce the strip to a substantially compact, non-porous form.

Although the present invention has been described in conjunction with preferred embodiments, it is to be understood that modifications and variations may be resorted to without departing from the spirit and scope of the invention, as those skilled in the art will readily understand. Such modifications and variations are considered to be within the purview and scope of the invention and appended claims.

I claim:

1. In a rolling mill adapted for the direct rolling of metal powder to fiat metal strip in widths exceeding about one inch in width comprising compacting rolls and a hopper above said rolls for holding powder to be rolled by passage through said rolls, the combination with said hopper of hoods above said rolls forming the lower face of the hopper and being shaped to conform with the shape of the compacting rolls and being adjacent to said rolls, said hoods having edges concave in form and so constructed that said edges are further apart in the region of the centers of the roll working faces than in the region towards the edges of said working faces whereby metal strip can be produced which is characterized by decreased frilling at the edges upon subsequent sintering, cold r011- ing and annealing.

2. In a rolling mill adapted for the direct rolling of metal powder to fiat metal strip in widths exceeding about one inch in width comprising compacting rolls and a hopper above said rolls for holding powder to be rolled by passage through said rolls, the combination with said hopper of hoods above said rolls forming the lower face of the hopper and being shaped to conform with the shape of the compacting rolls and to contact said rolls, said hoods having hood edges concave in form and so constructed that said edges are further apart in the region of the centers of the roll working faces than in the region towards the edges of said working faces whereby a greater amount of powder is fed during operation through the rolls adjacent the centers of the roll working faces than towards the edges of the rolls to produce metal strip characterized by substantial freedom from frilling at the edges upon subsequent sintering, cold rolling and annealing.

References Cited in the file of this patent UNlTED STATES PATENTS 187,588 Blake Feb. 20, 1877 2,758,336 Franssen Aug. 14, 1956 2,771,637 Silvasy et al Nov. 27, 1956 FOREIGN PATENTS 631,485 Germany June 20, 1936 379,283 Great Britain Aug. 23, 1932 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No, 2,922 189 January 26, 1960 Roy Philip Perks It is hereby certified that error appears in the above 'ring correction and that the said Letters numbered patent requi Patent should read as corrected belowo In the heading to the printed specification insert the following:

" Claims priority application Great Britain May 29 1956 line 31, for "operation" read operations e column 1,

7th day of December 1960? Signed and sealed this 2 (SEAL) Attest:

KARL H, AXLINE ROBERT C; WATSON Commissioner of Patents Attesting Officer after line 10 

